Measurement and Correlation of Water Activities and Refractive Indices for the Systems PPG425 + (NH4)2SO4 + H2O and PPG425 + Na2SO4 + H2O at 298.15 K

The water activities and refractive indices of the systems polypropylene glycol (PPG425) + (NH 4 ) 2 SO 4 + H 2 O and PPG425 + Na 2 SO 4 + H 2 O were measured at 298.15 K. The water activities were obtained using the isopiestic method. The water activities and refractive indices data were correlated with empirical equations. The agreement between the correlation and the experimental data is good.